The present invention relates generally to seat pads and more particularly to an improved pressure distribution pad for wheelchairs.
Conventional seat pads are often made from a generally solid material such as foam rubber or an equivalent plastic foam material. Less solid pads have incorporated a gel material or similar semi-viscous substance. Still less solid pads have included liquid filling the entire pad or disposed in individual compartments thereof. While these pads provide more comfort than a flat hard surface to a person seated thereon, there still does not result a desired type of support in that the reaction of the pad is uniform over the entire surface and the seated individual tends to shift or roll from side to side or from forward to rearward positions. Thus there is a certain degree of "instability."
To overcome this problem, it has been proposed to provide pads which are contoured and which are made of compositions which have a "memory". In both instances, it is usually required that the seated individual remain in the same position all the time in order to realize the best pressure distribution. In other words, the pressure points must remain within the contoured areas if the pad is to be effective.
Hall, U.S. Pat. No. 3,987,507, describes a pad assembly of resilient foam material having interior cutout portions at locations corresponding to those locations at which maximum pressures are typically exerted by a person seated on the pad assembly. These cutout portions are filled with a foam material of lesser density than the remainder of the pad assembly. Unlike those pads utilizing liquids, semi-vicous gel materials or simple foam rubber or plastic foam, the design of this resilient foam pad is such that there is no tendency to develop shear forces or for a patient to "roll" on the pad. Thus the design is such that the patient is not only "stable", but the patient is not confined to one position as would occur with a contoured cushion or one of the type incorporating a memory pad.
However, the Hall pad assembly has not proven to be entirely satisfactory in use. First, the density of the filler foam material placed in the interior cutout portions at the factory may not be the most suitable for use in those particular positions for particular patients. Second, even when the filler foam material placed in the interior cutout portions was of the most suitable density for a particular patient at the original time of usage of the assembly, as the patient's body undergoes changes over time that particular density at a later date may no longer be the most suitable. For example, the patient's weight may vary radically, bedsores or other skin irritations may appear or disappear, the amount of time that the patient will spend on the pad daily may vary, etc. Thus the need remains for a pad assembly of resilient foam material which can be manufactured so as to provide an initial customized level of support within the interior cutout portions and which can easily be modified as required over time, without return to the factory, so as to provide a different level of support within one or more of the interior cutout portions.
Accordingly, it is an object of the present invention to provide a pressure distribution pad assembly in which the density of the filler foam material in the interior cutout portions may easily be varied initially after receipt from the factory to meet the particular needs of the individual user.
Another object is to provide such an assembly in which the density of the filler foam material in the interior cutout portioms may easily be varied over time, without return to the factory, in order to meet the changing requirements of the individual user.
A further object is to provide a kit from which such assemblies can be easily constructed and modified outside of the factory.
It is also an object to provide a pressure distribution pad which, by varying the foam density in different sections, helps control posture.